Here's #26! Click here for the master list!
Animal Man #26
This was a real tough choice, as the pick boiled down to either Grant Morrison's final issue of Animal Man and the first appearance of the New Teen Titans in DC Comics Presents #26.
The real problem is that both books pass the "do people remember this issue number years later?" test, which a lot of other notable first appearances fail (like Mary Marvel's first appearance, for instance). People DO remember that DC Comics Presents was the first New Teen Titans and people DO remember that Animal Man #26 was the last issue of Grant Morrison's run where Morrison, himself, interacts with Animal Man.
Ultimately, I am going with Morrison's issue because I think the remembrance of the Animal Man issue is a bit "purer," as a real key to people remembering DC Comics Presents #26 (which was only a 16-page preview of the book) was the fact that it was WORTH something during the 1980s and early 1990s. People remember Animal Man #26, however, because it was an issue that jumps out when people think of the number #26, so while it certainly is not much of an edge, I think it IS a real edge.
And besides, it's nice to have an issue of Morrison's great Animal Man run on the list, anyways!
Other notable #26s...hmmm...Bendis' Daredevil run began with #26, Moore had a good one on Saga of the Swamp Thing, same with Gaiman on Sandman, but nothing all that standout. Same with Kirby/Lee on FF and Ditko/Lee on Amazing Spider-Man - just good, solid issues.